Language learning system and a digital storage unit

ABSTRACT

Audio recordings and programs are saved as audio files on a digital storage unit in a language learning system comprising student units connected to the digital storage unit. The digital storage unit is provided with a audio interface controller ( 201 ) having a dedicated input/output RAM buffer (B 1 -B 63 ) for each student station. Each RAM buffer has an associated file which is either a fixed file or can be defined for each case. When the audio interface controller ( 201 ) receives a record command relating to a specific buffer, the controller ( 201 ) opens an audio file associated with the specific buffer, buffers the audio data received from a student station or another source in the buffer, and transfers the contents of the specified buffer to the opened associated audio file. Similarly, in response to a play command relating to a specific RAM buffer, the controller ( 201 ) opens an associated audio file in the digital storage unit, transfers audio data from the opened audio file to the buffer, and sends the audio data from the buffer to a respective student station or to other destination.

[0001] The invention relates to interactive language learning systems.

[0002] Language laboratory systems relate generally to systems whoseobject is to train students in hearing and speaking a foreign languagein a classroom environment. Language laboratory systems or languagelearning systems typically comprise a teacher station and a number ofstudent stations connected to the teacher station. The most conventionalsystems employ a tape recorder as memory means for storing teachingmaterial and student's speech. The teacher station also allows theteacher to control all program sources and student recorders, choicegroups and pairs, monitor student activity and contact an individualstudent, group of students or the whole class. The student can reproducehis recorded voice in order to compare it with the model pronunciationand to monitor his/her progress in learning.

[0003] More recent language learning systems employ, instead of a taperecorder, an electronic (digital) recording storage means, such assemiconductor memory.

[0004] U.S. Pat. No. 5,065,317 discloses a language laboratory systemwherein a plurality of student training stations are connected to adigital storage device. Headsets in the training stations are connectedby input and output analog audio signal lines to dedicated A/D-D/Aconverters in the digital storage device. Further, a control panel ofthe training stations are each hardwired with a dedicated pair of analogcontrol lines to a control unit in the digital storage device, one ofthe lines carrying a record command signal and the other line carrying areproduction command signal. The digital storage device includes also avoice memory having a plurality of storing partitions. The digitalstorage device comprises also an address memory which stores thestarting address data and terminating address data which designates thestarting and terminating ends of the storing partition in which thevoice information data received from the A/D converter is stored. Forexample, when the control unit receives a record command signal from atraining unit over the respective control line, the control unit storesthe voice information data obtained from the A/D converter in acorresponding storing partition of the voice memory. The control unitalso stores in an address memory a pair of starting address data andterminating address data of the corresponding storage areas of thestoring partition in which the voice information data is stored. On theother hand, when one of the reproduction command signals having apredetermined level, for example, a level representing a logic “1” issupplied to the control unit, the control unit reads one of the pairs ofstarting address data and terminating address data from the addressmemory and, using these starting and terminating address data, a controlunit further reads a memorized voice information from the storage areain the storing partition of the voice memory which is designated by theread starting and terminating address data. The read voice informationdata is D/A converted into an analog audio signal which is then suppliedto the student training station over a dedicated signal line.

[0005] A problem related to this prior art language laboratory systemusing a digital memory storage is a very complicated management of thestored material in the memory. The prior art system is also a closedsystem in the sense that importing of teaching and program material tothe storage unit and exporting of student recordings from the storageunit is not possible. More-over, a high number of multi-wire cables arerequired.

[0006] An object of the invention is a new type of language learningsystem using a digital storage.

[0007] This object of the invention is achieved by a language learningsystem and a digital storage unit as defined in the attached independentclaims. Preferred embodiments of the invention are defined in theattached dependent claims.

[0008] In the present invention, audio recordings and programs are savedas audio files on a digital storage unit in a language learning systemcomprising student units connected to the digital storage unit. However,normal ways to create and handle audio files are not sufficient for timecritical (real time) recording and playing. Therefore, the digitalstorage unit is provided with a audio interface controller having adedicated input/output RAM buffer for each student station. In otherwords, each buffer can be seen as an input or an output to the massmemory in the storage unit. Each RAM buffer has an associated file whichis either a fixed file or can be defined for each case. In specialcases, the same file can be associated with several of the buffers. Whenthe storage unit receives a record command relating to a specificbufferit opens an audio file associated with the specific buffer,buffers the digital audio data received from a student station oranother source in the buffer, and transfers the contents of thespecified buffer to the opened associated audio file. In response toreceiving a stop command, the storage unit stops the ongoing recordingand closes the associated file. Similarly, in response to a play commandrelating to a specific RAM buffer, the storage unit opens an associatedaudio file in the digital storage unit, transfers audio data from theopened audio file to the buffer, and sends the digital audio data fromthe buffer to a respective student station or to other destination. Inthe, preferred embodiment of the invention, the audio file consists ofinteger numbers of buffer size blocks, and full data blocks are read orwritten. In other words, digital audio data is transferred from thebuffer to the associated audio file, when the buffer is filled up byreceived audio data. Similarly, full block of audio data is transferredfrom the audio file to the buffer, and new block is not transferreduntil all data in the previous block has been sent to the destination.If recording is stopped when a RAM buffer is only partially filled,according to an embodiment of the invention the partially filled buffercontent is transferred to the file, file is closed and informationrelating to the length of the partially block is saved. In anotherembodiment block sizes smaller than the buffer size are employed. In thepreferred embodiment of the invention, the transfer from the buffer tothe associated file, and vice versa, is carried out as a direct memoryaccess (DMA) transfer.

[0009] The input/output buffer enable a high speed recording and playingof audio material together with use of audio files for saving therecordings. In the preferred embodiment the audio data and commands aresent in data packets over an audio network, such as an audio local areanetwork (ALAN). The student station can be very simple, typically itneeds only acoustic/electrical transducers (e.g. headset with amicrophone), A/D and D/A converters, the user interface for inputtingcommand (e.g. a keyboard and optionally a display), and a communicationinterface for packet mode communication with the digital storage unitover the audio network. As a consequence, the manufacturing cost of thepanel is very low. Further, due to the packet mode communication used,the audio network can be implemented with minimum cabling. The use ofthe audio files in the digital storage unit allows to use standard massmemories, such as hard discs, which reduces the cost of the storageunit. The special purpose memories and complicated memory controldisclosed in the U.S. Pat. No. 5,065,317 is avoided. Further, as therecordings and teaching material are saved in audio files in the storageunit, it is possible to apply normal file management operations ofcomputers to these audio files. In an embodiment of the invention, thedigital storage unit comprises a server entity enabling audio files insaid storage unit being managed by normal file management operationsfrom a computer workstation. This enables for example a teacherworkstation to load recorded student audio files from the digitalstorage unit and/or save media files in the digital storage unit to beplayed by the student stations.

[0010] The invention will be now described in more detail by means ofpreferred embodiments with reference to the accompanying drawings, inwhich

[0011]FIG. 1 illustrates a learning system according to an embodiment ofthe invention,

[0012]FIG. 2 is a block diagram of a media storage unit,

[0013]FIG. 3 illustrates RAM buffers, audio files, and a DMA transferbetween the buffers and files, and

[0014]FIG. 4 illustrates a data packet format.

[0015] The system components of a language learning system according topreferred embodiment of the invention is illustrated in FIG. 1. Thelearning system comprises a number N of student audio panel 2 ₁. . . 2_(N), audio source 5, teacher audio panel 6 and a media storage unit(MSU) 1 interconnected via an audio network, such as an audio local areanetwork 4. In the embodiment shown in FIG. 1, the audio network 4comprises a connection unit 3 having a plurality of connection ports 31to which the student audio panels, the media storage unit 1, the audiosource 5, and the teacher audio panel 6 are connected by cable into astar network configuration. The language learning system furthercomprises a teacher computer workstation 7 (e.g. ordinary PC) connectedto the media storage unit 1 via a normal LAN or cable 8.

[0016] Student audio panels 2 ₁ . . . 2 _(N) and the teacher audio panel6 are provided with a headset 9 (i.e. earphones and a microphone) whichis connected to the audio panel. The audio panels perform the necessaryanalog-to-digital (A/D) and digital-to-analog (D/A) conversions to theanalog audio signal from the microphone and to the digital audio signalreceived over the audio network 4, respectively. The audio panels 2, 6further include a user interface, e.g. a keyboard and a display, forentering commands and displaying messages. The audio panels 2, 6 furtherinclude a communication interface for sending and receiving commands,messages and digital audio data in data packets. The panels 2, 6 areconnected to the connection unit 3 using cables 10, such as Ethernetcables, which also supply electrical power to the audio panels 2, 6 fromthe connection unit 3 so that no power source is needed in the audiopanels.

[0017] Audio source 5 provides an input for an external program source.In case a analog external program is inputted, the audio source 5provides the necessary A/D conversion. Also the audio source 5 includesa communication interface for sending and receiving digital audio datain data packet over the audio network 4. The audio source 5 may alsoinclude a audio line output for supplying an analog audio signal to anexternal device. The audio source 5 may also include a D/A conversionfor providing the analog output signal. The external program sourceconnected to the audio source 5 may be any suitable audio source. InFIG. 1, a sound card SC of teacher workstation 7 is connected the audiosource 5 by a cable 11. This allows any audio program from a audio CD, amedia file, etc., which can be played at a normal workstation by meansof a sound card, also be played to the student audio panels and recordedto the media storage unit as a master program, when the audio signal issupplied to the audio source 5 and sent in data packets over the audionetwork 4. Other examples of possible external audio sources are MP3player, cassette recorder, etc.

[0018] All the communication over the audio network 4 is packet modecommunication. The data packet may have a format illustrated in FIG. 4.In the preferred embodiment of the invention, the data packets containprimarily ASCII characters for easier monitoring and debugging. Binarydata is presented in HEX ASCII. The parts of the data packet are START(contains one character), ADDRESS (contains four characters, 12 bits),IDENTIFIER (at least one character) which defines the type of message orcommand code, DATA field, CHECKSUM (two characters), which may be asimple bit sum of eight bits (may be using XOR operation), and END (onecharacter). The connection unit 3 carries out all the mixing and routingfrom one audio panel 2, 6 to another, and between the audio panels 2, 6and the media storage unit 1. The mapping between the port numbers and avariety of devices 1, 2, 5 and 6 connected to the ports 31 isestablished when the system is set up. It may be possible to modify thisconfiguration from the teacher workstation via the media storage unit 1as will be explained later. In the preferred embodiment of theinvention, the teacher workstation 7 is also able to modify the routingtables in the connection unit so as to provide different student pairsor groups for practices. The data transmission bandwidth between thestudent audio panel and the connection unit may be, for example, 1 Mbpsfor audio and 16 kbps for control data. Assuming that 32 audio panelsare connected to the connection unit, the data transmission bandwidthbetween the connection unit 3 and the media storage unit 1 may be, forexample, 4 Mbps for control data and 32 Mbps for audio. The audiobandwidth supported is preferably 15 kHz or higher. The digital audiodata provides many advantages, such as a high signal-to-noise ratio(SNR), high immunity to external interference, and the audio qualitybeing unaffected by the length of the student cable 10.

[0019] The media storage unit 1 provides a storage for teaching program(master) and student recordings. A block diagram of a media storage unitaccording to an embodiment of the invention is shown in FIG. 2. In thepreferred embodiment of the invention the mass memory in the mediastorage unit 1 is provided by a hard disc drive (HDD) 202. It ispreferably a normal HDD manufactured for personal computers or servers.The media storage unit (MSU) 1 has also an audio network interface 200to the audio network 4, such as an Ethernet interface. All the datapackets received from the audio network 4 are forwarded from theinterface 200 to an interface controller 201. In the opposite direction,data packets supplied by the interface controller 201 are sent via theinterface 200 to the audio network 4.

[0020] The interface controller 201 includes a plurality of RAM buffers,two for each audio panel connectable to the audio network 4. Each RAMbuffer functions as an input to or an output from an associated file inthe HDD 202, depending on whether the audio data is recorded to the fileor played from the file.

[0021] Referring to FIG. 3, 64 buffers B0, B1, B2, . . . B62, and B63are shown in the interface controller 201. Let us assume, that buffersB0 and B1 are assigned to student audio panel 2 ₁, buffers B2 and B3 areassigned to student audio panel 2 ₂, etc. The buffers with unevennumbers, i.e. B1, B3, B5, . . . B63 are buffers for recording andplaying student voice. The audio files associated with these buffers B1,B3, . . . B63 are fixed, i.e always the same files. In FIG. 3, thesefixed files are illustrated by files B1.Wav, B3.Wav, . . . B63.Wav. Thebuffers with even number, i.e. buffers B0, B2, . . . B62, are intendedfor recording the master program, typically played from the externalaudio source called a master. Audio files associated with buffers B0,B2, . . . B62 are variable (can be defined for each case). This allowsalso that the same file can be associated with two or more buffers B0,B2, . . . B62. In FIG. 3, the audio file Eng 99 Spring.WAV is associatedwith a buffer B0. The audio file master.WAV is associated with both thebuffer B2 and the buffer B62. The audio data is transferred from thebuffers B0-B63 to the associated files and from the associated files tothe buffers by means of a DMA (direct memory access) transfer. Eachaudio file in the HDD 202 consists of integer number of data blockshaving a size equal to or smaller than the buffer size. The buffer sizemay be for example 128 kb, which represents two seconds of audio whensampling rate of 32 kHz and resolution of 16 bits is used. The buffersize may be dynamically variable. In the preferred embodiment only fullblocks of 128 kb are written from the buffers to the files or read fromthe files to the buffers. Only if the recording is stopped when a RAMbuffer is only partially filled, the content of the partially filledbuffer is transferred to the file and the length information of theshorter data block is saved.

[0022] The interface controller 201 provides various recorder operationsaccording to commands received from the audio panels 2, 6 or from theteacher workstation. The three basic recorder operations are

[0023] PLAY fills the specified RAM buffer from a pre-defined disc file,

[0024] RECORD transfers contents of the specified RAM buffer to apredefined disc file,

[0025] PAUSE pauses ongoing data transfer,

[0026] STOP stops ongoing recording or playing and closes the file.

[0027] The commands supplied to the interface controller 201 associate afile with a buffer and define a direction of the data transfer, i.e.playing/recording. Commands also cause the interface controller 201 tostart playing or recording a buffer(s) and associated file(s). In thefollowing, examples of possible commands are listed.

[0028] Record master only causes the interface controller to record aspecified buffer to a specified file. For example, content of buffer B4is transferred to the audio file Eng 99 Spring.WAV.

[0029] Record master and students cause an interface controller 201 torecord a specified master buffer to a specified file. For example, thecontent of buffer B0 is transferred to the file Eng 99 Spring.WAV. Thecommand also cause the interface controller 201 to record the studentbuffers B1, B3, . . . B63 to corresponding fixed files B1.WAV, B3.WAV.B63.WAV, respectively.

[0030] Record students only cause the interface controller to record thestudent buffers B3, B5, . . . B63, to the corresponding fixed files,B3.WAV, B5.WAV, B63.WAV, respectively.

[0031] Play master only causes the interface controller 201 to fillspecified buffers from a specified (master) file. For example, buffersB2 and B62 are filled from the audio file master.WAV.

[0032] Play students only will cause the interface controller 201 tofill the named student buffers B1, B3, . . . B63 from the correspondingfixed files B1.WAV, B3.WAV, . . . B63.WAV.

[0033] Play master and students will cause the interface controller 201to fill the specified ones of the master buffers B0, B2, . . . B62 fromthe specified file, such as the master.WAV, and to fill the namedstudent buffers B1, B3, . . . B63 from the corresponding fixed filesB1.WAV, B3.WAV, . . . B63.WAV.

[0034] Let us now consider recording to and playing from the hard discfiles by means of examples. Let us assume that the interface controlleris commanded to record from the RAM buffer B1 to the audio file B1.WAV.The interface controller receives data packets from the student audiopanel 2 ₁ over the audio network 4 and the audio interface 200. Thesedata packets contain an address assigned to the buffer B1. Therefore,the interface controller inputs the payload in the data field of thedata packets to the buffer B1. Having filled the buffer B1 with theaudio data received in the data packets, the interface controller 201transfers the content of the data buffer 1 as a single data block to theaudio file B1.WAV in the hard disc 202. Then the interface controller201 starts to refill the buffer B1 with the received audio data. Therecording is continued until a stop command is received or a maximumsize of the audio file is reached. In response to the stop command, theinterface controller 201 stops inputting new audio data to the buffer B1but transfers the content of the partially filled buffer B1 to the fileB1.WAV and closes the file. The interface controller also saves lengthinformation of the last data block.

[0035] Let us then assume that the interface controller 201 has receiveda command to play audio data from the audio file B1.WAV to the bufferB1. The buffer B1 is filled with a first data block of the buffer sizetransferred form the file B1.WAV. Interface controller 201 inserts theaudio data from the buffer B1 to data fields of data packets which areaddressed to the student audio panel 2 ₁, and sends these data packetsto the audio network 4. When the buffer 1 has been emptied, a new datablock of buffer size is transferred from the file B1.WAV to the bufferB1, and the previous operation is repeated. This continues until theinterface controller 201 receives a stop command or all data in theaudio file B1.WAV has been read.

[0036] The file format of the audio files may be any suitable format,but WAV format is preferred.

[0037] The media storage unit 1 includes also another communicationinterface 204, preferably TCP/IP interface, for communication with theteacher workstation 7 over the normal LAN/cable connection 8. Theinterface 204 is connected to a server entity 203 and to the interfacecontroller 201. The server entity 203 provides a server function whichenables the workstation 7 to perform normal file management operationsto the hard disc drive 200 in a similar manner as to any disc within theworkstation or in a normal LAN. These file management operations includeat least loading and saving a file. As the files created and/or used bythe interface controller 201 are standard files, the server entity 203allows to load these files to the teacher workstation and to save newmedia files to the HDD to be used as internal master program sources.This makes the media storage unit 1 as a open system which is a majorbenefit in comparison with the prior art closed digital memory systems.

[0038] The teacher workstation 7 can also communicate with the interfacecontroller 201 and further with the connection unit 3 or the audiopanels 2, 6 via the interface 204. All commands or data addressed to theinterface controller 201 or to the devices in the audio network 4 arerouted from the interface 204 to the interface controller 201. If theinterface controller receives a command addressed to itself, it reactsaccordingly. If a data or command is destined to the connection unit 3,or one of the audio panels, the interface controller sends the data orcommand to the target device in the data packets. Similarly, any data orcommand received from the audio network 4 and addressed to the teacherworkstation is forwarded to the workstation 7 via the interface 204 bythe interface controller 201. This enables the teacher workstation tosend messages and commands to any device in the system and to configurethe system for different exercises.

[0039] The teacher workstation 7 may include a system manager functionSM and a graphical user interface GUI for managing and controlling ofthe system.

[0040] In an embodiment of the invention the graphical user interface isbased on an activity approach. An activity means a pre-defined lessonplan for exercise, e.g. Listening comprehension and model imitation. Theuser interface software has some activities as default lesson plans. Forexample, a list of activities shown in the user interface may includeone or more of the following: listening comprehension; model limitation,read allowed exercise; phone conversation; pair discussion; groupdiscussion; simultaneous interpreting; consecutive interpreting; recordresponse; and quiz test. In the activity approach, the teacher canselect an activity he/she wants the students to accomplish. The activitycan be directed to all the students or to a group of students. The userinitiates an activity for a session, that is, for a group of students.In response to the selection of activity, a panel appears on the userinterface which contains all the control needed in proceeding theselected activity. The session panel may include the followingfunctionality: 1) student selection; 2) activity selection; 3) sourceselection; 4) starting the activity; 5) ending the activity.

[0041] The activity (procedure) is a kind of a template for the lesson,since the session panel is structured to follow the steps of the actualactivity procedure. The activities are very easy to modify.Additionally, new activities are very easily added to the userinterface. At a time, only those controls are visible/enabled which areneeded in the particular phase of the activity.

[0042] Although the present invention has been described with respect topreferred embodiments, various changes and modifications which areobvious to person skilled in the art are deemed to lie within the spiritand scope of the invention.

1. A language learning system comprising a plurality of student audiostations (2 ₁-2 _(N)) connected to a digital storage unit (1), saidstudent stations (2 ₁-2 _(N)) being able to independently store audiorecordings to and play stored audio recordings from said storage unit(1), characterized in that said digital storage unit (1) comprises adedicated input/output RAM buffer (B0-B63) for each student station (2₁-2 _(N)), an audio interface controller (201) responsive to a recordcommand for opening an audio file in said digital storage unit (1), forbuffering audio data received from a student station (2 ₁-2 _(N)) in therespective one of said dedicated buffers (B0-BN) and for transferringthe contents of the buffer to said opened audio file, said audiointerface controller (201) being responsive to a play command foropening an audio file in said digital storage unit (1), for transferringstored audio data from said opened audio file to a respectiveinput/output buffer (B0-B63), and for sending said audio data from saidrespective buffer (B0) to a respective student station.
 2. A system asclaimed in claim 1, characterized in that audio signals and commandsbetween the student stations (2 ₁-2 _(N)) and said digital storage unit(1) are transferred in data packets over an audio network (4).
 3. Asystem as claimed in claim 1 or 2, characterized in that said audiointerface controller (201) comprises a dedicated second input/output RAMbuffer (B0, B2 . . . B62) for each student station for recording amaster program played from another source (5) into a respective secondspecified file and/or playing a recorded master program or a saved mediafile from said respective second specified audio file.
 4. A system asclaimed in claim 3, characterized in that said dedicated pair of RAMinput/output buffers (B0-B63) of each student can be controlled torecord simultaneously, to play simultaneously, or one buffer to recordand the other buffer to play to and/or from separate audio files.
 5. Asystem as claimed in claim 1, 2, 3 or 4, characterized in that saiddigital storage unit (1) comprises a server entity (203) enabling audiofiles in said storage unit (1) to be managed by normal file managementoperations from a computer workstation (7).
 6. A system as claimed inclaim 5, characterized in that said workstation (7) is a teacherworkstation, and said file management operations include loadingrecorded student audio files from said digital storage unit (1) and/orsaving media files in said digital storage unit (1) to be played by saidstudent stations (2 ₁-2 _(N)).
 7. A system as claimed in claim 5 or 6,characterized in that said workstation (7) is connected to said digitalstorage unit (1) over a network (8) other than said audio network (4).8. A system as claimed in any one of claims 1 to 7, characterized inthat audio network (4) comprises a connection unit (3) comprising adedicated port (31) for each of said student stations (2 ₁-2 _(N)) andsaid digital storage unit (1), said connection unit (3) being configuredto route said data packets between said student stations (2 ₁-2 _(N))and said digital storage unit (1).
 9. A system as claimed in claim 8,characterized in that said connection unit (3) is reconfigurable by ateacher workstation (7) either directly or via said digital storage unit(1).
 10. A system as claimed in any one of claims 1 to 9, characterizedin that said digital storage unit (1) comprises a memory device (202),such as a hard disc, for storing said audio files.
 11. A system asclaimed in any one of claims 1 to 10, characterized in that said playcommand and/or said record command is received from a respective studentstation (2 ₁-2 _(N)) or from a teacher's computer workstation (7).
 12. Asystem as claimed in any one of claims 6 to 11, characterized in thatsaid teacher workstation (7) has a graphical user interface (GUI) whichemploys an activity approach in controlling the learning activities. 13.A digital storage unit for a language learning system comprising aplurality of student audio stations (2 ₁-2 _(N)) connected said digitalstorage unit (1), said storage unit (1) storing audio recordings andplaying stored audio recordings for said student stations, characterizedin that said digital storage unit (1) comprises a dedicated input/outputRAM buffer (B0-B63) for each student station (2 ₁-2 _(N)), means (201)responsive to a record command for opening an audio file in said digitalstorage unit (1), for buffering audio data received from a studentstation in the respective one of said dedicated buffers and fortransferring the contents of the buffer to said opened audio file, means(201) responsive to a play command for opening an audio file in saiddigital storage unit (1), for transferring stored audio data from saidopened audio file to a respective input/output buffer (B0-B63), and tosend said audio data from said respective buffer to a respective studentstation (2 ₁-2 _(N)).
 14. A unit as claimed in claim 13, characterizedin that audio signals and commands between the student stations (2 ₁-2_(N)) and said digital storage unit (1) are transferred in data packetsover an audio network (4).
 15. A unit as claimed in claim 13 or 14,characterized by a dedicated second input/output RAM buffer (B0, B2 . .. B62) for each student station for recording a master program playedfrom another source (5) into a respective second specified file and/orplaying a recorded master program or a saved media file from saidrespective second specified audio file.
 16. A unit as claimed in claim15, characterized in that said dedicated pair of RAM input/outputbuffers (B0-B63) of each student can be controlled to recordsimultaneously, to play simultaneously, or one buffer to record and theother buffer to play to and respectively from separate audio files. 17.A unit as claimed in any one of claims 13 to 16, characterized in thatsaid digital storage unit (1) comprises a server entity (203) enablingaudio files in said storage unit (1) to be managed by normal filemanagement operations from a computer workstation (7).
 18. A unit asclaimed in claim 17, characterized in that said workstation (7) is ateacher workstation, and said file management operations include loadingrecorded student audio files from said digital storage unit and/orsaving media files in said digital storage unit to be played by saidstudent stations.
 19. A unit as claimed in claim 17 or 18, characterizedin that said workstation (7) is connected to said digital storage unit(1) over a network (8) other than said audio network (4).
 20. A unit asclaimed in any one of claims 13 to 19, characterized in that saiddigital storage unit (1) comprises a memory device (202), such as a harddisc, for storing said audio files.